Cavitation Pressure Pulse Analysis

The Problem

Hydrodynamic cavitation induced by the acceleration of a fluid causes the local static pressure to drop to the fluid vapour pressure. Vapour bubbles are then instantaneously developed and travel along with the fluid. Once the bubble reaches a higher pressure zone, the vapour bubbles violently collapse, creating high intensity pressure and temperature pulses. This provides a powerful mechanism to break down unwanted elements and is the basis upon which the geometrical features of cavitation units are designed. However, to optimise the geometrical design, one requires some sort of measurement of cavitation.

The Approach

The measurement of cavitation can be obtained from a hydrophone. One of which, was employed in this work. This allowed the actual pressure pulses produced by the cavitation to be monitored in ‘real-time’ over a range of different cavitation units. As an additional step a Fourier analysis was carried out on the fly in order to analyse the power spectrum emitting from the device.

The Result

The ‘real-time’ monitoring and control system provided instant measurements of performance by measuring acoustic energy release. The analysis gave an in-depth insight into the magnitude and frequency of pressure pulses emitting from each of the cavitation devices tested. This allowed development of a suitable design which increased the frequency of cavitation events 5-fold and the magnitude of pressure pulses 10-fold with no additional energy input.